1. Preliminary Results from a Trial Beam Test of the Small HBD Prototype at LEGS Bob Azmoun BNL HBD Working Group Meeting May 10, 2005

2. 5/10/05Bob Azmoun, BNL2 Test Beam Layout The beam was studied extensively, so that the apparatus could be precisely aligned. Trigger = H1+S1+S2 Veto Cut Applied Off-line (although ~95% of e-’s are vetoed, this Veto provides for a very clean e- trigger, and removes all tracks that have associated showers, produced somewhere along the e- trajectory) LEGS e - Tagger Cave 64 Ch. e - Hodoscope S1 S2 Veto Tagged ~2 GeV e - Beam H1 ~50cm CF 4 Radiator CsI 3-GEM 3x3 pad array (~1.5”x1.5” ea.) Retractable VUV Lamp Retractable Fe-55 SS Vessel LEGS Cherenkov Counter w/ ~2” Lucite Veto pulse height Spectrum 1 e- 2 e- 3 e- The spectrum depicts single, double and triple particle showers passing through the veto scintillator.

3. 5/10/05Bob Azmoun, BNL3 Gas Quality Before and After Test Expect ~34pe’s Water “peaks” The Vessel was pumped on for two days, and purged for ~two weeks before the test The simple gas sys. (gas cyl.+flow-meter+bubbler) used for the test was purged at high flow for two days. The det. was sealed and transferred to LEGS, attached to the gas sys. and purged for ~5 hrs. There were no means to test the gas quality during the test, however we did test the gas quality before and after the test, under more or less the same conditions (i.e., similar purging period and flow rates).

4. 5/10/05Bob Azmoun, BNL4 GEM PC QE Measurement Three Weeks Before Test GEM PC was stored in questionable conditions (sealed vessel filled with N2) for two weeks prior to the test, and may have suffered some deterioration in its QE (???). The last time the GEM PC was measured, its integrated QE was half that of the nominal value. Ratio of the Area under each (Red/Blue) trend line = 2.0

5. 5/10/05Bob Azmoun, BNL5 Photoelectron Coll. Efficiency Vs E D Forward Bias: E D = +1.2kV/cm Reverse Bias: E D = -0.3kV/cm  ~ 0.9nA/1.0nA = 90% coll. eff.

6. 5/10/05Bob Azmoun, BNL6 Gain measurement Before During and After Test The GEM was operated with the WIS Volt Divider w/ Vin=4200, which corresponds to a Gain ~ 6000 - 7000 (as measured at LEGS and in the lab, using Fe-55).

7. 5/10/05Bob Azmoun, BNL7 All 9 Pads: E D = +1.2kV/cm Central Pad: E D = +1.2kV/cm, Veto Cut Expected primary charge from dE/dx: dE/dx MIP = 7keV/cm * 2.44mm / (54eV/e - -ion pair) = 31.6 e - ’s For ~2GeV e - ’s  Relativistic Rise factor: 31.6*1.4 = 44 e - ’s Measured primary Charge from dE/dx: At Gain of ~6500, Landau Mean ~ 45e-’s This result is derived from a “Quick Analysis”,where the Landau mean was roughly approximated…a more rigorous analysis will be done shortly

8. 5/10/05Bob Azmoun, BNL8 Mean number of Cherenkov pe-’s measured: Instead of adding pulse heights event by event for all the pads, a rough approximation of the mean number of total photoelectrons is calculated by summing the mean pulse height for each pad…a more rigorous analysis will be done shortly. The SUM of the avg. number of pe - ’s contributed from each pad = 16.25pe - ’s (Gain=6500) Correcting for known Detector Inefficiency’s 1.6% loss of primary pe-’s due to absorption in gas 2.Integrated QE is low by a factor of 2.0 3.pe Collection Efficiency ~90% Corrected # of pe-’s = 16.25 * 1.06 * 2.0 * (1/0.9) = 38 pe ! (Remember, this is a rough approx.) The final measurement shows a lot of promise! = 2.0 = 1.8 = 1.0 = 1.4 = 6.9 = 0.9 = 0.8 = 0.7 Note: The data presented in the histograms above is not the data set that was analyzed, and is meant to give an overall qualitative idea of the data, rather than act as an exact reference. All 9 Pads: E D = -0.3kV/cm

9. 5/10/05Bob Azmoun, BNL9 Next, Full Scale Test will include… GEM PC with nominal QE Need Large Glove Box to accommodate Det. for installation of CsI PC Water and Oxygen Analyzers Ordered New Panametrics Analyzers (arriving shortly) Utilize Flash Lamp During Test to test the PC, and/or the gas transmittance. The Test is scheduled to take place either this June or July